Measure time-resolved emission spectra of Prodan and Laurdan in DPPC vesicles with 0, 4, 8% di-palmitoyl glycerol. Spectra are obtained at several temperatures near the tm of DPPC (41.5!c) and as a function of added lysolecithin and fatty acid. The purpose is to determine the relationship between there additives and the accessibility and mobility of water molecules to the region of the bilayer occupied by the probes.